Does stress enhance or impair selective attention? The effects of stress and perceptual load on negative priming

Two negative priming (NP) experiments investigated the effects of stress and load on selective attention. In Experiment 1, in which stress was relatively low under all conditions, load was manipulated with two levels of prime-target discriminability. The NP effect was smaller in the high- than in the low-load condition. Experiment 2 contained both a low-stressed group and a high-stressed one. For each group, half of the trials were with low-load primes and half with high-load ones, as in Experiment 1. As in Experiment 1, with low stress, NP was reduced in the high- as compared to the low-load condition. However, with high stress, the effect was in the opposite direction. There was more NP in the high- than in the low-load condition. The cross-over interaction between the effects of load and stress on NP suggests that stress increases interference from irrelevant information, and thus, impairs selective attention.